What is Alpha particles?
Alpha particles (also termed alpha radiation or alpha rays) was the first nuclear radiation to be discovered (beta particles and gamma rays were identified soon after), they are produced by the alpha decay of a radioactive nucleus.
Because the nucleus is unstable a piece of it is ejected, allowing the nucleus to reach a more stable state.
The piece that is ejected is the alpha particle, which is made up of two protons and two neutrons: this is the nucleus of the helium atom.
Helium is an inert and harmless gas, so the particles are not dangerous in themselves, it is only because of the high speeds at which they are ejected from the nuclei that make them dangerous. At these high speeds, they have enough energy to break bonds in the matter or ionize atoms (knock electrons off), which is especially deleterious for living cells.
How do alpha particles affect the body?
The health effect from exposure to alpha particles depends greatly on how a person is exposed. Alpha particles lack the energy to penetrate even the outer layer of skin, so exposure to the outside of the body is not a major concern. Inside the body, however, they can be very harmful. If alpha-emitters are inhaled, swallowed, or get into the body through a cut, the alpha particles can damage sensitive living tissue. The way these large, heavy particles cause damage makes them more dangerous than other types of radiation.
The ionization they cause are very close together – they can release all their energy in a few cells. This results in more severe damage to cells and DNA.
How Alpha particles are formed?
Many alpha emitters occur naturally in the environment.
For example, alpha particles are given off by radionuclides such as uranium-238, radium-226, and other members of the naturally occurring uranium, thorium and actinium decay series which are present in varying amounts in nearly all rocks, soils, and water.
Artificially produced sources of alpha particles include the radioisotopes of elements such as plutonium, americium, curium, and californium.
These are generally produced in a nuclear reactor through the absorption of neutrons by various uranium radioisotopes.
We also have the ones produced by thorium and actinium decay series which are present in varying amounts in nearly all rocks, soils, and water.
What are alpha particles used for?
Alpha particles have low penetrating power but this still provides a range of useful applications:
smoke detectors – americium-241 is commonly used in ionizing smoke detectors.
The smoke that enters the detector reduces the number of alpha particles that are detected and triggers the alarm.
Static eliminators typically use alpha particles from polonium-210 to remove static charges from equipment.
Radioisotope thermoelectric generators use alpha particle decay from plutonium-238 to generate heat which is converted to electricity, commonly used in space probes.
Some alpha emitters are being investigated for their potential use in unsealed source radiotherapy to treat cancer.